The AN/TPN-22 system supports three modes for landing. Mode I is for remote control or fully automatic landings. Mode II involves the use of guidance commands to incoming aircraft. Mode III represents traditional landings with controllers on the ground directing aircraft. AN/TPN-22, with its ability to support these three types of landings, is part of the Marine Air Traffic Control and Landing System, or MATCALS. This automatic all weather system is a component of the larger Marine Air Command and Control Systems, or MACCS.
Part of the AN/TPN-22 system is an antenna. it sends out a pencil beam that operates on the I-beam frequency. It has a track-while-scanning feature that employs phase/frequency scanning. The antenna consists of 94 diode phase shifters and 94 arrays. These digital phase shifters are the mechanism by which the approach control system scans and detects incoming aircraft. The system of phase shifters and arrays uses the concept of circular polarization. That concept sends out the beam in all directions in a circular manner thus ensuring that no areas in the scanned region are missed. It provides total coverage even in bad weather.
The transmitter in the AN/TPN-22 approach control RADAR contains a Traveling Wave Tube. Its operation requires a power supply with high voltage. A TWT is an amplifier that increases the radar signal utilizing high power. In addition to the TWT, the system contains a modulator. It is solid state and serves the purpose of evening out the signal and reducing all loss. Modulating a signal is a process in radar technology that ensures that signals that travel a long way have their integrity restored. This provides the controller with an accurate and strong signal.
One feature of the AN/TPN-22 is its mobility. This allows it to be used by the Marines at remote landing sites . An example of such a site is Bogue Field, North Carolina. It provides a means to land tactical aircraft at Bogue Field with its track-while-scan radar.
